The present invention concerns the manufacture of optical transmission cable elements made of a mechanically supporting core surrounded by a dielectric coating with helical grooves in which optical fibres are freely laid and more particularly a device for laying the optical fibres in the grooves. The present invention is directed to the simultaneous laying of one optical fibre in each of the grooves in a structure of general cylindrical form of a type such as described in French Pat. No. 2,358,666 filed on Dec. 30, 1975 and U.S. Patent Application Ser. No. 877,872 filed on Feb. 15, 1978 for: "Cable incorporating optical fibres".